The background description provided herein is for the purpose of generally presenting the context of the invention. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
In robotics research, visual simultaneous localization and mapping (SLAM) can be applied in many different areas, including ground robots, augmented reality (AR)/virtual reality (VR), three-dimensional (3D) reconstruction, unmanned aerial vehicles (UAV), etc. Depending on computational resource, a visual SLAM can use sparse or dense features method for pose estimation. A sparse SLAM system uses sparse feature in its obtained images, and includes steps of feature detection, feature description, feature matching, motion computation, trajectory optimization, loop closure detection, mapping, localization, etc.
Lots of sparse features are stored in a bag-of-words structure during feature detection and description, and serve as landmarks in close loop detection. When close loop detection is activated, the system checks through the bag-of-words to find a similar feature and links the new position with the old position. Based on the linked position relation, the system uses bundle adjustment to optimize the whole trajectory and correct the map. However, searching features in a large bag-of-words structure is costly and slow; on the other hand, a small bag-of-words has a limited feature storage, and cannot represent the landmarks and is prone to resulting in false matches.
Other methods have also been developed to solve movable object problem, like frequency map enhancement (FreMEn). These methods use statistical principle to obtain a movable obstacle by computing its appearance likelihood, but the methods require the robot to map the target area multiple times with a time period.
Therefore, an unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.